Cutting beveled teeth.



PATENTED JUNE 12, 1906.

L. BOISARD. CUTTING BBVBLED TEETH.

APPLICATION FILED AUG. 25, 1904.

3 SHEETSSHEET 2 FIG vvivirwcss s J1; mm;

UNITED STATES.

PATENT OFFICE.

Specification of Letters Patent.

Patented June 12, 1906.

Application fiaa August 25,1904. SBIIEINO- 222,156.

To a w/mm it may concern:

1 Be it known that 1, Louis BOISARD, a citizen of the French Republic, residing at Lyon,

France, have invented certain new and useful Improvements in Cutting Beveled Teeth,

of which the following is a specification.

This invention relates to the automatic cutting of bevel-gears by means of helicoidal milling-cutters,

ro. In the annexed drawings, Figuresl and 2 are dia rams illustrating the cutting of the teeth of spur-wheels by means of a helicoidalmilling-cutter. Figs. 3, 4, and 5 are diagrams illustrating the application of the same principle to the cutting of the teeth of beveled wheels. Figs. 6 and 7 are elevation and plan, respectively, of the helicoidal milling-cutter for cutting beveled teeth according to this invention. Figs. 8 and 9 are fur- 2o ther diagrams of beveled wheels. Fig. 10 is a diagram illustrative of certain rocking movements to be given to the milling-cutter to obtain roper rolling contactrofiles to the beveled teeth out thereby. li ig. 11 is a side elevation, Fig. 12 a plan, and Figs. 13

and 14 end elevatlons, of a machine for cutting the gears based upon the principles here matter more particularly described.

In cutting gear-wheels by means of a heli- 0 coidal milling-cutter placed so that the axis of the helix of the, cutter is tan ential to a circle concentric with the whee that is being cut the cutter and the wheel are revolved at such relative speeds "v and V, respectively,

that the cutter makes a revolutions for each revolution of the wheel having a teeth, the

pitch of the helix bein equal to the dpitch of the teeth. This may e represente by the r'ormulaf%; This action is illustrated in Fig. 1, in which a is the wheel, and b the cutter. (Shown in diagram only.) The series of cutting-teeth followin one another at intervals along the line of t e helix is continued 5 through three or more complete coils c of the helix, in order to give to the teeth the proper profile for correct rolling action. It is essential also ,to give the cutter a movement of translationin a direction e d arallel to the axis of the wheel,as shown in ig. 2, in order that it may act in due course equally along the faces of the teeth over the whole thickness of the wheel. In applying the same principle, however, to the cutting of beveled wheels the difiiculty arises that as the pitch varies in proportion to the distance from the apex of t e cone f, Fig. 3, a cutter suitable, for example, to work at any one diameter 9, Fig. 3, is unsuitable at other diameters, for if the cutter has the pitch 0, Fi 1, suitable, with three coils, to work simu taneously on the faces of three teeth at diameter 9 any movement of this cutter toward the base of the cone f would cause it to out too deeply onto the two outer teeth and so destroy them, and, similarly, movement toward the apex of the cone would cause it to miss the two outer teeth and even attack the two teeth lying be- I yond them and so destroy the latter.

The resent invention comprises a helicoidal mi ing-cutter in which the series of cutters do not extend through more than one convolution of the helix or less and with which other means are provided for obtaining such movement as is necessary to 'ive the correct rolling profile to the teeth whlch would have been given by the convolutions that have been omitted.

Figs. 6 and 7 re resent a helical cutter is with a single threa formin only a part of a whole convolution, the pitc of which corresponds, for instance,with the smallest pitch 0 a given bevel-wheel having it teeth. The

cutter must make a revolutlons during one complete revolution of the cone. The cutter, penetrating to the proper extent into the cone, will exactly divide the circumference into a parts, producing in the cone n grooves corresponding to the thickness of the thread.

If the cutter is caused to travel toward the.

base of the, cone through a path parallel with the enerator of thelatter, the groove cut by it w 1 become larger, the enlargement being a function of the pitch of the helix, the distance traveled on the generator of the cone, and

the number n of teeth. Given these factors, it will therefore only be' necessary to leave on the cutter the number of teeth q corresponding to that portion of thehelix which 1 calculation based onthe said factors will indicate.

P the itch at the largest part of the cone,

and t e length of one tooth. The baseof the tooth must have the breadth e at the smallest part of the cone and the. breadth E mentioned above.

at the largest art of the cone. The pitch of the helix equa s With regard to the action of the helix at t e circumference of the large base during the fraction 20f a revolution of the cone the base of the tooth on the cone travels through P, while the pitch of the helix travels through 1). The base of the tooth will therefore be enlarged by the difference P 1), since part of the cone slides past the cutter. This must, however, only take place to the extent of E-e. If, therefore, C is a complete convolution of the helix, only a portion thereof equal to C X be operative. With this helical cutter, the development of the thread of which is equal to the value indicated, an exact division of the cone into n, perfectly uniform pyramidal teeth can be effected; but a section of any one of these teeth in a plane perpendicular to the base of the pyramid is not limited by the curves desirable as rolling surfaces. The usual way of effecting this is to work with as many convolutions on the helix as there are teeth in enga ement in the gear. This is impracticable witl i beveled gears, as Since the generators of the cone are at an les, it would be necessary to use an extensibTe cutter, which would be difficult to obtain. It is more simple to proceed in the followin manner: Let m-.n, Fig. 10, be the axis 0 the cone. The trajectory of the helix will be 1projected on the same line, 0-1) will be t e inclination of the projection of the next tooth above the first tooth, and q-r the projection of the next tooth below thefirst tooth. When the first tooth is made in the direction of the axis mn, the cutter is moved from m to 0 to the must extent of exactly one-pitch space, and a second cut is made along the trajectory 0 Then a third cut is made along g-r. 1 h practice the manner in which successive cuts are made at the desired intervals of space is very simple. It is sufiicient after making the cut parallel to m 'n to place the cutter at the summit of the cone and to give to the slide which guides the cutter the angleof inclination of the first tooth above that of the center and then the angle ofinclination of the first tooth below that of the center. By this means the average direction of the 'cuttingpart of the helix'during the first cut is caused to coincide with the axis mm During the second cut this directiontfollows the axis 0 1), and during the third cut it follows the axis q-r. In practice these three cuts will be sufficient; but fui ther passes may also be made corres onding respectively, to the second tooth ahove orbelow. the center if rolling contact extends 'overfive teeth. By this means any'desired degree of precision with regard to 'the limiting revolution curves of the teeth can be obtained. It may be mentioned that in practice sufficient accuracy will be obtained if the cut along the line m-n is dispensed with, only theother two cuts being used.

The machine for carrying out the method described must comprise means for adjusting the cutter and. the cone and for imparts ing the various movements required, namely: first, the rotation of the-cutter; second, the rotation of the cone to be cut; third, the displacement of the cutter along a generator of the cone at the roots of the teeth out.

Six adjustments must be provided for, namely: (a) The adjustment of the cone with regard to the direction of its axis, so that the generator at the roots of the teeth is parallel to the path of the cutter; (b) the adjustment of the cone in such a manner that when its axis has been placed in the proper direction its summit is placed in the trajectory of the cutter; (c) the adjustment of the cutter with regard to the angle of inclination of its axis, so that the average direction of movement of the cutting part of the helix is at the proper angle with regard to the plane containing the axis of the cone and the cone-generator in question; ((1) the adjustment of the slide su porting the cutter in such a manner that t e trajector of the cutter lies in the desired directions uring the different cuts (e) the relative adjustment of the number of revolutions made by the cutter and the cone, re-

of the invention.

The machine comprises a. frame A, which supports all the parts. The step-pulley B, which is driven by any suitable means, trans mits movement by means of the cardanj oint C to the worm D. The latter drives the helical cutter G b means of the worm-wheel E and the shaft The Worm H, integral with the ulley- B, drives the worm-wheel I and the s aft J the movement of the latter being transmitted, by means of the gear-wheels K K, mounted in the arms L L, to the bevelpinions M and M. With the pinion M the inions N and N can be separately thrown mto gear. The pinions N and N are keyed to the shaft 0, to the end of which is fixed the bevel-pinion P, meshing withthe wheel P. the Worm Q, which drives the worm-wheel Q, and the cone to be cut is fixed to the axle of the said worm-wheel Q. To the axle R of the inion M is fixed the step-pulley S, which rives, by means of the belt T, the step pulley S. The latter is integral with the The axle of the latter is provided with IOO worm U, which drives the worm-wheel U. The movement of the worm-wheel U is transmitted by means of the cardan-joint V to the worm X, which drives the Worm-wheel X. The latter is internally screw-threaded and mounted on the screw Y, which is fixed to the cutter-slide Z and adapted to impart to the latter longitudinal movement along the generator of the cone. The three principal movements being obtained in the manner described the regulation and adjustments are effected as follows:

(a) The adjustment of the axis of the cone in such a manner that the generator of the cone is parallel to the path of the cutter is effected by means of the worm A and wormwheel A. When the part B which is integral with the worm-wheel A, has been adjusted in the desired position, it is fixed to the frame A by means of the screws C C (1)) The longitudinal adjustment of' the cone in such a manner that after its axis has been placed in the desired direction its suinmit is in the trajectory of the cutter is effected by means of the worm D which is operated by means of a hand-wheel, the axle of which is rotatable, but not longitudinally movable in the bearing D fixed tothe art 15*. The worm D engages the nut E, w iich is fixed to the slide F When the latter has been adjusted in the desired position, it is fixed to the part B by means of the screws F (0) The adjustment of the cutter with regard to the direction of its axis in such a manner that the average direction of the cuting part of the helix isat the desired angle with regard to the plane containing the coneaxis and the. generator in question is effected by means of the toothed segment G Fig. 14, fixed to the cutter, this segment-being operated by means of the worm 1 mounted on the slide Z, supporting the cutter. When the shaft F has been adjusted, as desired, the cutter-holder is fixed to the slide Z by means of the screws J 2 and K (d) The adjustment of the slide supporting the cutter in such a manner that the trajectory of the cutter follows the angle indicated by the diagram is obtained by rotating the slide L about the axle M by means of the worm N and worm-wheel N the latter being fixed to the said slide L When the desired angle has been obtained, the slide L is fixed, by means of the nuts 0?, to the plate P, which forms part of the frame A.

(a) The desired ratios between the number of revolutions made by-the cutter and the cone, respectively, is obtained by means of the train of change-gear K K, the slotted bearing-arms L L of which are rotatable about the axles J and R. x

(f) The velocity with which the cutter is longitudinally displaced is as a rule regulated by changing the gear-train K K; but a coarse adjustment is effected by means of the belt T and the step-pulleys S and S.

All the adjusting-wheels referred to are provided with verniers to indicate even the smallest movements. The oil by means of which the cutter is liberally lubricated descends onto the horizontal part of the frame A and flows through a channel surrounding the table of the frame to the receptacle Q from which it is returned to the cutter by means of a pump.

Although the machine described is specially designed for the cutting of bevel-gears, it can also be used for other purposes, more particularly for cutting conical cutters.

I claim, in means for cutting beveled teeth- 1. The combination of a helical cutter having a pitch equal to that of the teeth to be cut at the small diameter of the cone and having a development equal to a fraction of a convolution of the helix, means for displacing the cutter parallelly to the generator of the cone, and means for giving relative simultaneous rotation to cutter and cone according to the equation V 2. The combination of a helical cutter having a pitch equal to that of the teeth to be cut at the small diameter of the cone and having a development equal to a fraction of a convolution of the helix, means for giving relative simultaneous rotary movements to the cutter and cone according to the equation V=Z, means for displacing the cutter parallelly to the generator of the cone, and means for displacing the cutter in such relation to the teeth as to bring the latter to the desired profile for rolling contact by a plurality of passes.

3. The combination of a cone-blank holder of a helical cutter having a pitch e ual to that of the teeth to be cut at the smal diameter of the cone and having a development equal to a fraction C E helix, the axis of said cutter lying in a plane perpendicular to that of the cone, means of relative displacement of said cone-holder and cutter whereby the cutter follows a generator of the cone and means for giving relative simultaneous rotation to the cutter and coneof a convolution of the holder according to the equation V In witness whereof I have signed this specification in the presence of two witnesses.

LOUIS BOISARD.

Witnesses:

GUILLAUME PIoonE, HIPPOLYTE VILLELONGUE 

